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Poster: JeffT Date: Dec 4, 2009 9:47am
Forum: movies Subject: Sound synchronization problems

Several videos I'm uploaded recently have sound synchronization problems in the derived flash versions. I thought this problem was fixed, but it seems to have come back.

http://www.archive.org/details/Oakland_raw_food_meetup_2009_12_03_Panel
http://www.archive.org/details/Redwood_Center_2009_11_20_Charles_Cadieu

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Poster: Administrator, Curator, or Stafftracey pooh Date: Feb 4, 2010 2:02pm
Forum: movies Subject: Re: Sound synchronization problems

hi jeff,
first, not to be too nitpicky, but we dont make flash derivs -- only h.264 mpeg-4 derivs (as i'm pretty sure you know). we merely use the flash plugin as an "A/V file player" 8-)

In most (maybe even all?) of the items of yours that I have come to see have A/V sync issues, when i look at the deriver log, i see things like this when opening/analyzing your file:
# [mov,mp4,m4a,3gp,3g2,mj2 @ 0x29a0000]multiple edit list entries, a/v desync might occur, patch welcome

so it makes me wonder -- are these coming straight off a vid cam w/o processing with something like finalcut pro (et al)? and if so, does the cam allow for "start/stop" pause where the file continues on writing to on big file?
are you doing start/stop pause at all? if so, how do you make the big single files we see uploaded?

--tracey


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Poster: JeffT Date: Feb 4, 2010 3:59pm
Forum: movies Subject: Re: Sound synchronization problems

Hi Tracey,
I usually (90% of time) edit the files using MPEG Streamclip to trim the beginning and merge files that are larger than 4GB (which is the largest size file the camcorder stores). MPEG Streamclip is free, runs on Mac and, I think, Windows. In summary, my production process is:
1. Record the video. Done using Sanyo Xacti HD1010 Camcorder. Records onto flash memory. I usually use the "HD-SHQ" mode, which is 1280x720, 30FPS. The format recorded is "MPEG-4 AVC/H.264" (that's what's written on the camcorder).
2. Remove the SD card from the camcorder and plug it into a USB adapter connected to MacBook.
3. Run MPEG Streamclip, load the video files into it, and edit out unnecessary parts at the beginning of the clip, also merge files if there are more than one.
4. Save the edited file from MPEG Streamclip onto disk.
5. Upload to Archive.org.

Could the problem be with MPEG Streamclip? Would you like me to do a test, that is, uploading a short clip with and without being edited by MPEG Streamclip?

p.s. Thanks for the clarification about the derived flash. I did have a misconception.

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Poster: Administrator, Curator, or Stafftracey pooh Date: Feb 4, 2010 4:22pm
Forum: movies Subject: Re: Sound synchronization problems

hi Jeff!

yah! i mean, i'm not 100% sure why ffmpeg is glitching at -- but it seems to be consistent across various OS and releases of it for testing i've done.

so yes, i think it might be helpful to try a "raw" video -- maybe for one that was A/V sync issued and see if any happier? if it's fine then, not 100% sure what that might mean for you/us -- but at least we'd be getting somewhere! 8-)

-tracey

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Poster: JeffT Date: Feb 4, 2010 6:27pm
Forum: movies Subject: Re: Sound synchronization problems

I uploaded some test videos (about 3 minute long video of a clock). Processing by MPEG Streamclip does introduce about a one second difference in the synchronization. If it causes a problem here, maybe it's causing worse problems in other cases. Videos are:

Raw video:

http://www.archive.org/details/Xacti1010_raw_test_2010_02_04

Raw video, just read and written by MPEG Streamclip (no editing). Sound sync still seems fine:
http://www.archive.org/details/Xacti1010_raw_test_2010_02_04_stream_clip_passthrough

This time, trim first 26 seconds of video using MPEG Strimclip "In" timeline feature. Introduces about a one second difference in the sync:
http://www.archive.org/details/Xacti1010_trim_test_2010_02_04

Try again, use "In" feature followed by "Trim" edit command. One second difference in sync is still about the same:
http://www.archive.org/details/Xacti1010_trim2_test_2010_02_04